Abstract HIV can be effectively managed if people with HIV are identified and their virus is controlled by therapy. However, many HIV-infected people do not know their HIV status, so increased access to testing is needed. In addition, therapy can fail due to drug resistance or lack of adherence to therapy schedules, and tests are needed to identify when therapy is failing for either reason. We will develop a test to diagnose HIV and detect treatment failure that is simple enough for users to test themselves. Aim 1. HIV-specific capture for sample preparation. We will develop a sample preparation system that directly targets HIV virions via endogenous human antibodies bound to the virion surface, human markers on the envelope, and HIV virion epitopes. Aim 2. Core assay development. We will develop an isothermal amplification assay for HIV and design an internal amplification control. Aim 3. Fast and sensitive detection for HIV diagnosis. This work will build on core assay development (Aim 2) but add enhancements for fast and sensitive amplification and detection and develop the core paper device. In addition, we will test a hypothesis that test sensitivity can be increased by contribution of HIV genomic targets from the cellular fraction. Aim 4. Semi-quantitative test for viral rebound detection. We will build upon preliminary results showing threshold-based detection to develop a semi-quantitative test that reports a yes/no for a single threshold and can be ready by eye. Aim 5. Device design, integration, and scale up for clinical testing (R33 Phase). In this Aim, we will refine the design for robust operation, evaluate performance and reproducibility in-house, and scale-up to produce devices for clinical testing. Aim 6. Clinical testing in the US and South Africa (R33 Phase). We will evaluate the tests on fresh fingerstick blood at clinical sites in Seattle, USA and Durban, South Africa to evaluate performance as a primary diagnostic test (1 and 2) and as a test for virologic failure (3 and 4) by comparison to FDA-cleared tests.